We have a Carrier electric forced air furnace (older model circa 1988) is making a high pitched humming/vibrating noise (worse upon starting/kicking on) and a continual mechanical/electrical smell coming through the ducts/vents. We replaced the filter and fan motor capacitor. It is blowing out heat and responds to change in thermostat. It takes a few minutes to shut down after switching off system at thermostat. Any thoughts or other troubleshooting ideas? Thanks

I had this type of smell in my home a few years ago and it turned that the fan was past it's prime and was overheating, causing the burnt smell in my home.

It does sound like the windings are starting to break down from overheating. The smell is the varnish and sometimes people in the trade refer to it as askrill. It is what they coat the electrical windings with at the motor manufacturer. The varnish is placed on the windings to prevent short circuits in the motor BUT when the motor starts to overheat from age/end of service life that is when it sterts to smell. Time to go out and buy a motor and change it out.